In the oil and gas industries, some inverted electric submersible pump (ESP) systems that have the pumps below the motor use a special connection between the shafts that can transmit not only the torque but also the axial load. This axial load can arise from the thrust within the pumps, weight of the shafts and impellers below, or pressure difference in the sections acting on shafts. The axial load should be transmitted to the axial bearings located in the protector.
Similar axial load can appear in some conventional ESPs in situations in which the pump is operated for upthrust and this is transmitted to the protector by torque locking in the coupling.
Conventionally, connection of the shafts in inverted ESPs is mostly performed with the special “pinned” couplings that can be fixed to the shaft with a pin installed in a hole through the shaft and coupling. The pin transmits the axial load from the shaft below to the coupling and the second pin transmits the axial load from the coupling to the shaft above. Installation and removal of these pins has been difficult in the field, and in some cases they are impossible to remove.